I think I've figured it out

[DarkPenguin]

Poly only understands force. Makita on 5 and it works. Hand sanding is a non starter.

 

[Toulouse_Tuhles]

There is poly, and there is yet again... poly.  I've got some ultra hot clear here that hand sands like month old lacquer when its cured for only an hour!
Ya just gotta work with what ya got.  Different materials all need adapted technique!